In the microelectronics industry as well as in other industries involving construction of microscopic structures (e.g., micromachines, magnetoresistive heads, etc.), there is a continued desire to reduce the size of structural features. For example, in the microelectronics industry, the desire is to reduce the size of microelectronic devices and/or to provide greater amount of circuitry for a given chip size.
Effective lithographic techniques are essential for achieving reduction of feature sizes. Lithography impacts the manufacture of microscopic structures, not only in terms of directly imaging patterns on the desired substrate, but also in terms of making masks typically used in such imaging. Typical lithographic processes involve formation of a patterned resist layer by patternwise exposing a radiation-sensitive resist to an imaging radiation. The image is subsequently developed by contacting the exposed resist layer with a material (typically an aqueous alkaline developer) to selectively remove portions of the resist layer to reveal the desired pattern. The pattern is subsequently transferred to an underlying material by etching the material in openings of the patterned resist layer. After the transfer is complete, the remaining resist layer is removed.
For some lithographic imaging processes, the resist used does not provide sufficient resistance to subsequent etching steps to enable effective transfer of the desired pattern to a layer underlying the resist. In many instances (e.g., where an ultrathin resist layer is desired, where the underlying material to be etched is thick, where a substantial etching depth is required, and/or where it is desired to use certain etchants for a given underlying material), a so-called hardmask layer is used intermediate between the resist layer and the underlying material to be patterned by transfer from the patterned resist. The hardmask layer receives the pattern from the patterned resist layer and should be able to withstand the etching processes needed to transfer the pattern to the underlying material.
Also, where the underlying material layer is excessively reflective of the imaging radiation used to pattern the resist layer, a thin antireflective coating is typically applied between the underlying layer and the resist layer. In some instances, the antireflection and hardmask functions may be served by the same material.
Furthermore, device fabrication has migrated to 90 nm node and smaller for next generation chips. The resist thickness has to be thinner than 300 nm due to image collapsing problems, low focus latitude from high NA tool, and high OD of resist formulation in 193 and 157 nm lithography. Conventional thin resist films are not sufficient for etching processes. Therefore, there is a need to address this etch issue by adopting a bilayer silicon resist or a silicon ARC/hardmask approach. The spin-on hardmask provides a better solution than a CVD hardmask, due to the capability of planarization on top of different topography and ease of stripping. It is advantageous to use a ARC/hardmask system because the same single layer resist can be used, without the need of developing a new resist system containing silicon. Thinner resists can also be used in this ARC/hardmask approach to enhance the process latitudes observed in a typical silicon resist type bilayer approach.
While many hardmask and antireflective coating materials exist in the prior art, there is a continued desire for improved compositions. Many of the prior art materials are difficult to apply to the substrate, e.g., they may require the use of chemical or physical vapor deposition, and/or a high temperature baking process may be used in forming the same. It would be desirable to have antireflective coating/hardmask compositions that could be applied by spin-on coating techniques, without need for a high temperature bake.
Additionally, it is desirable to have hardmask compositions which can be easily etched selective to the overlying photoresist while being resistant to the etch process needed to pattern the underlying layer.
U.S. Pat. No. 6,420,088 and co-pending and co-assigned U.S. application Ser. No. 10/124,087, filed Apr. 16, 2002, the disclosures of which are incorporated herein by reference in their entirety, describe a polymer system containing Si—O components in silsesquioxane polymers. The Si—O polymer has etch characteristics similar to silicon dioxide.
Despite the description of Si—O polymers, there is a need for providing new and improved polymer compositions that can be used in photolithography which have etch characteristics that are similar to Si.